The personal identification system is described in Patent Literature 1. This personal identification system includes a light source, an imaging unit, and an image processing unit. A plurality of light-emitting elements, which make the foregoing light source, are arranged according to a shape of a finger. The foregoing light-emitting element is a near-infrared high-intensity LED or a laser beam.
The above-mentioned personal identification system operates as follows.
The foregoing light source outputs a weak light for detecting the finger at any time. The foregoing imaging unit detects whether or not the finger is exposed to the weak light. When it is detected that the finger has been exposed to the weak light, the foregoing light source decides which element of the light source is turned on based upon this finger location information. The foregoing light source acquires pixel value information of the image that is being monitored by the foregoing imaging unit, and optimizes the amount of light to be supplied from the light source. The foregoing imaging unit, after this optimization of the amount of light to be supplied, captures an image of an imaging object (living body). The foregoing image processing unit performs the following image correction (contour extraction/image rotation processing) for the image captured by the foregoing imaging unit. That is, the foregoing image processing unit firstly performs an edge emphasizing processing for the captured image, and extracts the contour position of the finger. The foregoing image processing unit performs the rotation processing based upon this extracted contour so that the finger inclination becomes constant. FIG. 18 shows an example of the contour extraction/rotation processing. FIG. 18(a) is a view illustrating the finger subjected to the contour extraction, and FIG. 18(b) is a view illustrating the finger subjected to the rotation correction.
The operation of the authentication is performed through the calculation of correlation to find a similarity between a blood vessel pattern image of the finger registered in advance and a blood vessel pattern image of the finger captured by the imaging unit. An authentication result is obtained by performing a threshold processing for the value obtained by the correlation calculation.